The present invention relates generally to outboard motors, and more particularly, to a throttle assembly having a deadband engagement.
In general, internal combustion engines include at least one cylinder constructed to receive combustion gases that pass through an air intake opening formed in a throttle body attached to the engine. Typically, the amount of combustion gas provided to the cylinder is partly controlled by the position of a throttle plate. As an operator desires increased output from the engine, the operator advances a throttle actuator which in turn opens the throttle plate thereby providing increased amounts of combustion gas to the cylinders. In addition to mechanically actuating the throttle plate, the throttle actuator also initiates increased fuel supplied to the cylinders. In fuel injected engines, the throttle actuator signals an ECU to increase an amount of fuel supplied to the cylinders by a fuel system and, in carbureted engines, the throttle actuator mechanically provides more fuel to the cylinders. As an operator increases the engine speed from idle, the throttle plate gradually opens an amount that is generally proportional to the operator initiated change in throttle actuator position thereby providing more combustion gas to the cylinders of the engine.
As the throttle plate opens in response to the throttle command, in addition to allowing more combustion gas, or air, to pass into the engine, increased amounts of engine noise are allowed to exit the engine through the throttle body and past the throttle plate. Additionally, some known throttle plates have holes formed therethrough. These holes provide an appropriate amount of combustion gas necessary for idle operation of the engine. Those throttle plates which have holes formed therethrough, may cause a whistling, or chirping sound. Alternatively, the throttle plate is held open to allow sufficient air to pass by to maintain idle speed. Those that are held open generally allow engine noise to pass unobstructed. Combustion noise allowed to exit the engine via the air intake, in addition to any whistling or chirping caused by the throttle plate idle holes, can be a distraction to an otherwise well-performing engine. Additionally, a quieter operating engine that eliminates any noise is generally advantageous.
Modern engines often include an integration of a plurality of electrically controlled components. These components can include fuel injection systems, oil injection systems, combustion timing systems, and cooling systems to name a few. These systems are often controlled, in part, by an electronic control unit (ECU). One sensor connected to the ECU is a throttle position sensor (TPS). Commonly, the TPS communicates the position of the throttle plate relative to the throttle body opening, often referred to generically as the air intake, through a series of linkages. By communicating to the ECU the position of the throttle plate, the ECU can calculate the amount of combustion gas passing through the throttle body. By knowing the amount of combustion gas provided to the engine, the ECU can more effectively control the amount of fuel provided to the cylinders as well as ignition timing in order to optimize the operating efficiency of the engine.
Generally, as an operator increases or decreases the throttle actuator, generically referred to as an accelerator, the ECU, via the TPS, measures the throttle input commands and can regulate engine operation in response thereto. Excessive tolerance in the linkage between the throttle actuator and the throttle plate can make the precise determination of the throttle plate position difficult to ascertain. As such, although the ECU is receiving a signal from the TPS indicative of a throttle plate position, because of play in the linkage, the throttle plate may not be at the exact position indicated by the TPS. As such, the operation of the engine may not be optimized because of the interdependency of these systems on the actual throttle plate position. Additionally, the engine may not be as responsive to throttle input commands as desired.
It would be therefore be desirable to have an engine with a throttle assembly that reduces the amount of noise emitted from the main air intake. To this end, it would be desirable to operate the engine with the throttle plate in a closed position for a range of throttle actuator inputs. It would also be advantageous to reduce play between the throttle actuator and the throttle plate and obtain more accurate throttle plate position indicators.